Ideal wound dressing materials should be active components in the healing process. Bacterial cellulose (BC) has attracted a great deal of attention as novel wound dressing materials; however, it has no intrinsic antimicrobial activity. To explore the practical application values of BC and develop novel wound dressing materials, a series of composite membranes based on BC and polymeric ionic liquids (BC/PILs, composed of BC, and PILs formed by choline and different amino acids) with antimicrobial activity were synthesized by an ex situ method. The physicochemical and antimicrobial properties and biocompatibility of these membranes were systematically investigated. The results indicated that BC/PIL membranes with excellent properties could be obtained by adjusting the concentration and type of PILs. Several kinds of BC/ PIL membranes exhibited good biocompatibility and high antimicrobial activity against Gram-positive and Gram-negative bacteria and fungus. The anionic PILs played important roles in the antimicrobial activity of BC/PIL membranes. The obtained membranes provided a novel promising candidate for wound dressing materials.

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We model several Au/conjugated molecule/Au junctions in the presence of molecular geometrical torsions. A rectification ratio of around 10 in the twisty diphenyldipyrimidinyl system is obtained, which is in good agreement with experiment. Deeper insight into the rectification mechanism of the conjugated molecular diodes is presented on the basis of simulations in a set of simpler but similar junctions. The rectification effect (the ratio) is significantly improved with increasing the molecular twist, while the conductance is reduced accordingly. Our results suggest that the rectification can be enhanced by the geometrical-torsion-induced reduction in the conjugation length of organic molecules.

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Biofouling is a multifaceted and unavoidable problem in the application of membrane separation technology. Here, we functionalized polyvinylidene fluoride (PVDF) ultrafiltration membranes with poly­(ionic liquid) (PIL) brushes to provide them with antibiofouling properties. The PIL brush grafted membranes (PIL-M) were prepared via atom transfer radical polymerization (ATRP) using different ionic liquids (ILs) on the membrane surface. Four functionalized membranes with different alkyl chain lengths (C4-M, C8-M, C12-M, and C16-M) were prepared to explore the relationship between surface structure and antibacterial properties. Our results showed that all of the PIL-M had antibacterial capabilities with the highest efficiency of 84.6% for the C12-M. Moreover, the antibacterial performance was improved by increasing the ATRP reaction temperature and time. Liposome vesicles were used as the bacterial cell membrane model to evaluate the antibacterial membrane damage mechanism. IL and PIL brushes could damage cell membranes through disrupting the lipid bilayer with longer alkyl chains associated with an enhanced effect. Zeta potential measurements showed that the interference of electrostatic interactions with bacteria also played an important role in the bactericidal mechanism. Moreover, filtration experiments in a cross-flow system further indicated that PIL-M membranes have favorable antibiofouling performance, with a stable flux increase 41.7% larger than that of the pristine PVDF membrane. Our results suggest that functionalization of the membrane surface with the PIL brushes can effectively resist bacteria and thereby significantly mitigate biofouling on the PVDF membranes.

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